Hardware Lines or a Tiled Bitmap? - Which Method is the Fastest When Making a Grid?

[Franz Bazarov]

On AmigaOS 3.x, with original hardware, is it faster (at the machine level) to draw the actual lines themselves, or is it faster to tile a bitmap of a suitably pixel-stroked square, if one wanted to make a full-screen grid very quickly?

Reasons for both methods would be helpful.

Alternately, would it just be faster to load & display a full background image of a previously prepared full grid image?

Thanks!

[Zetr0]

I would say that using a small 2 bitplane tile for the grid would be the best, keeping the size divisible by 8 and use the blitter to slap (thats BlitBitMask) it to the background bitmap.

I would sugest this for a basic unexpanded 020 or lower (even with fast ram), however with an 030 CPU it would probably quicker to write the whole lot to a Screen Bitmap in fast ram and then just blast it to the current screen rasta bitmap.

[Leffmann]

You can get a grid on the screen virtually free as far as processing time goes, but it requires some hardware poking and is less flexible, and I'm assuming you will want to show some bitmap graphics on top of the grid as well.

Typically you will clear the whole bitmap when you redraw the graphics, and since copying with the blitter is just as fast as clearing alone you can just copy a prepared full screen grid in one go into the bitmap every time you want to change the graphics. This is flexible and straight forward, but it requires that your other graphics is drawn with respect to the grid, which can be slower than drawing with the assumption that the bitmap is clear.

You can also allocate 1 bitplane for the grid alone and use the other bitplanes for the graphics, and you won't need to redraw the grid or consider it when drawing the graphics.

What the fastest method is depends on what you want to show on top of the grid really.

[Franz Bazarov]

Thanks!

Basically, I want to prepare a number of monochromatic vector grids.

The background being a straight 2D grid, and the foreground being comprised of multiple perspective-shifted grids going off to a point on the horizon.

I want to set it up so that you can see through the grids with transparency, to give an illusion of huge depth. I'm planing on using dual playfields.

None of this will be texture mapped, it will appear like old school vector graphics (Tempest, Batttlezone, etc), meaning just lines in a 2D space (but projected to give an illusion of 3D space). Should perform well.

Other than that, alpha-numeric data & sprites will be in the foreground.

Once this display is setup, I want to be able to control small areas of the screen with borderless terrain generated polygonal or line-oriented mountains as seen on the Fairlight CMI Page D & Joy Division "Unknown Pleasures" album.

I want to maintain a very retro vector feel to the whole thing, but use various LED styled fonts in conjunction with a vector style engineering font that I've created.

As of now the fonts are Truetype, I'm going to look into a converter if needed, or else some static ones will be represented with bitmaps & the dynamic ones will be native Amiga.

There will be movement on some perspective grids, similar to the game "Ballblazer" on the Atari 8-bit, but it will be vector-style, not checkered.

That's about it. I'm thinking that I might do a combination of the three methods, when animation is necessary.

I'm doing some testing of prepared grid squares following the powers of two, from 4x4 through 1024x1024 to test fixed stepping zooms. Looks pretty cool!